Andrei Lihu, Jincheng Du, Igor Barjaktarević, Patrick Gerzanics · 5 authors
Bitcoin mining is a wasteful and resource-intensive process. To add a block of transactions to the blockchain, miners spend a considerable amount of energy. The Bitcoin protocol, named 'proof of work' (PoW), resembles a lottery and the underlying computational work is not useful otherwise. In this paper, we describe a novel 'proof of useful work' (PoUW) protocol based on training a machine learning model on the blockchain. Miners get a chance to create new coins after performing honest ML training work. Clients submit tasks and pay all training contributors. This is an extra incentive to participate in the network because the system does not rely only on the lottery procedure. Using our consensus protocol, interested parties can order, complete, and verify useful work in a distributed environment. We outline mechanisms to reward useful work and punish malicious actors. We aim to build better AI systems using the security of the blockchain.
Abstract A zero-knowledge proof or protocol is a cryptographic technique for verifying private data without revealing it in its clear form. In this paper, we evaluate the potential for zero-knowledge distributed ledger technology to alleviate asymmetry of information in the asset-backed securitization market. To frame this inquiry, we conducted market data analyses, a review of prior literature, stakeholder interviews with investors, originators and security issuers and collaboration with blockchain engineers and researchers. We introduce a new system which could enable all market participants in the securitization lifecycle (e.g. investors, rating agencies, regulators and security issuers) to interact on a unique decentralized platform while maintaining the privacy of loan-level data, therefore providing the industry with timely analytics and performance data. Our platform is powered by zkLedger (Narula et al. 2018), a zero-knowledge protocol developed by the MIT Media Lab and the first system that enables participants of a distributed ledger to run publicly verifiable analytics on masked data.
Sami Ben Mariem, Pedro Casas, Matteo Romiti, Benoît Donnet · 6 authors
Blockchains are typically managed by peer-to-peer (P2P) networks providing the support and substrate to the so-called distributed ledger (DLT), a replicated, shared, and synchronized data structure, geographically spread across multiple nodes. The Bitcoin (BTC) blockchain is by far the most well known DLT, used to record transactions among peers, based on the BTC digital currency. In this paper, we focus on the network side of the BTC P2P network, analyzing its nodes from a purely network measurements-based approach. We present a BTC crawler able to discover and track the BTC P2P network through active measurements, and use it to analyze its main properties. Through the combined analysis of multiple snapshots of the BTC network as well as by using other publicly available data sources on the BTC network and DLT, we unveil the BTC P2P network, locate its active nodes, study their performance, and track the evolution of the network over the past two years. Among other relevant findings, we show that (i) the size of the BTC network has remained almost constant during the last 12 months - since the major BTC price drop in early 2018, (ii) most of the BTC P2P network resides in US and EU countries, and (iii) despite this western network locality, most of the mining activity and corresponding revenue is controlled by major mining pools located in China. By additionally analyzing the distribution of BTC coins among independent BTC entities (i.e., single BTC addresses or groups of BTC addresses controlled by the same actor), we also conclude that (iv) BTC is very far from being the decentralized and uncontrolled system it is so much advertised to be, with only 4.5% of all the BTC entities holding about 85% of all circulating BTC coins.
Crowdsensing is an emerging paradigm of data aggregation, which has a pivotal role in data-driven applications. By leveraging the recruitment, a crowdsensing system collects a large amount of data from mobile devices at a low cost. The critical issues in the development of crowdsensing are platform security, privacy protection, and incentive. However, the existing centralized, platform-based approaches suffer from the single point of failure which may result in data leakage. Besides, few previous studies have addressed the considerations of both the economic incentive and data quality. In this paper, we propose a decentralized crowdsensing architecture based on blockchain technology which will help improve the attack resistance. Furthermore, we present a hybrid incentive mechanism, which integrates the data quality, reputation, and monetary factors to encourage participants to contribute their sensing data while discouraging malicious behaviors. The effectiveness our of proposed incentive model is verified through a combination of the theory of mechanism design. The performance analysis and simulation results illustrate that the proposed hybrid incentive model is a reliable and efficient mean to promote data security and incentivizing positive conduct on the crowdsensing application.
Abstract Blockchain and cryptocurrency are a hot topic in today’s digital world. In this paper, we create a game theoretic model in continuous time. We consider a dynamic game model of the bitcoin market, where miners or players use mining systems to mine bitcoin by investing electricity into the mining system. Although this work is motivated by BTC, the work presented can be applicable to other mining systems similar to BTC. We propose three concepts of dynamic game theoretic solutions to the model: Social optimum , Nash equilibrium and myopic Nash equilibrium . Using the model that a player represents a single “miner” or a “mining pool”, we develop novel and interesting results for the cryptocurrency world.
Wibson is a blockchain-based, decentralized data marketplace that provides individuals a way to securely and anonymously sell information in a trusted environment. The combination of the Wibson token and blockchain-enabled smart contracts hopes to allow Data Sellers and Data Buyers to transact with each other directly while providing individuals the ability to maintain anonymity as desired. The Wibson marketplace will provide infrastructure and financial incentives for individuals to securely sell personal information without sacrificing personal privacy. Data Buyers receive information from willing and actively participating individuals with the benefit of knowing that the personal information should be accurate and current. We present here two different components working together to achieve an efficient decentralized marketplace. The first is a smart contract called Data Exchange, which stores references to Data Orders that different Buyers open in order to show to the market that they are interested in buying certain types of data, and provides secure mechanisms to perform the transactions. The second is used to process payments from Buyers to Sellers and intermediaries, and is called Batch Payments.
The growing size of modern datasets necessitates splitting a large scale computation into smaller computations and operate in a distributed manner. Adversaries in a distributed system deliberately send erroneous data in order to affect the computation for their benefit. Boolean functions are the key components of many applications, e.g., verification functions in blockchain systems and design of cryptographic algorithms. We consider the problem of computing a Boolean function in a distributed computing system with particular focus on \emph{security against Byzantine workers}. Any Boolean function can be modeled as a multivariate polynomial with high degree in general. However, the security threshold (i.e., the maximum number of adversarial workers can be tolerated such that the correct results can be obtained) provided by the recent proposed Lagrange Coded Computing (LCC) can be extremely low if the degree of the polynomial is high. We propose three different schemes called \emph{coded Algebraic normal form (ANF)}, \emph{coded Disjunctive normal form (DNF)} and \emph{coded polynomial threshold function (PTF)}. The key idea of the proposed schemes is to model it as the concatenation of some low-degree polynomials and threshold functions. In terms of the security threshold, we show that the proposed coded ANF and coded DNF are optimal by providing a matching outer bound.
After introducing key concepts and definitions in the field of digital identity, this paper will investigate the benefits and drawbacks of existing identity systems on the road towards achieving self-sovereign identity. It will explore, in particular, the use of blockchain technology and biometrics as a means to ensure the “unicity” and “singularity” of identities, and the associated challenges pertaining to the security and confidentiality of personal information. The paper will then propose a model of blockchain-based self-sovereign identity based on attestations, claims, credentials and permissions, which is globally portable across the life of an individual. Such a system is not dependent on any particular government or organization for administration or legitimacy, although it might include government issued identification and biometrics as one of many indicia of identity. Such a solution based on a recorded and signed digital history of actions is a system that best approximates the fluidity and granularity of identity, enabling individuals to express only specific facets of their identity, depending on the parties with whom they wish to interact. This paper focuses on two case studies to explain how such a credentials system could work in specific contexts: (1) Kiva’s identity protocol for building credit history in Sierra Leone, and (2) World Food Programme’s Building Blocks program for delivering cash aid to refugees in Jordan. Finally, the paper will explore what the future might look like when blockchain-based cryptocurrencies and self-sovereign identity intersect. With digital transactions functioning as identity claims within an ecosystem based on self-sovereign identity, new business models might emerge, such as identity insurance schemes, along with the emergence of value-stable cryptocurrencies (“stablecoins”) functioning as local currencies.
Software-defined industrial network has emer-ged as an autonomous ecosystem where the network control relies on a centralized controller to provide seamless data transfer. However, the reliance on a centralized controller can lead to several challenges, such as single point of failure. An adversary can initiate a denial of service attack and limit the availability of the controller by projecting malicious or uncontrolled traffic flows. To overcome this, in this article, a deep-learning-based blockchain framework is designed for providing secure software-defined industrial network. In this framework, a blockchain mechanism is designed wherein all the switch are registered, verified (using zero-knowledge proof), and, thereafter, validated in the blockchain using a voting-based consensus mechanism. A deep Boltzmann machine based flow analyzer is deployed at the control plane to identify the anomalous switch requests. The evaluation is performed using a mininet emulator wherein the results obtained depict the superiority of the proposed framework.
The aim of this paper is to understand whether Distributed Ledger\nTechnologies (DLTs) are ready to support complex services, such as those\nrelated to Intelligent Transportation Systems (ITS). In smart transportation\nservices, a huge amount of sensed data is generated by a multitude of vehicles.\nWhile DLTs provide very interesting features, such as immutability,\ntraceability and verifiability of data, some doubts on the scalability and\nresponsiveness of these technologies appear to be well-founded. We propose an\narchitecture for ITS that resorts to DLT features. Moreover, we provide\nexperimental results of a real test-bed over IOTA, a promising DLT for IoT.\nResults clearly show that, while the viability of the proposal cannot be\nrejected, further work is needed on the responsiveness of DLT infrastructures.\n
Ingrid Bauer, Liudmila Zavolokina, Fabian Leisibach, Gerhard Schwabe
Blockchain technology is expected to create a variety of new opportunities for businesses. Yet, little is known about how the technology actually enables to create value and how companies will be able to exploit true business value. However, without a clear understanding of the value creation potential from the technology, and corresponding adaption of business practices, the realization of value is doomed to failure. Hence, we contribute to this gap by exploring and explicating the specificities of value creation from blockchain in the ecosystem of a car. In the course of an exploratory case study analysis, over a time period of 2 years, we conducted three iterations of interviews and workshops with industry and blockchain experts from five diverse stakeholder groups. In brief, we provide early evidence that (1) blockchain enables value creation through: Distributed Product Innovation, Shared Operational Efficiency, and Controlled Customer Intimacy. Furthermore, we discuss our learnings for businesses in other domains aiming to leverage value from blockchain technology. We do so, by deriving guidelines for each blockchain value discipline. Furthermore, we give recommendations on how blockchain projects in ecosystems should approach multiple blockchain value potentials.
Wei Wang, J. J. Song, Guangquan Xu, Yidong Li · 6 authors
Smart contracts are decentralized applications running on Blockchain. A very large number of smart contracts has been deployed on Ethereum. Meanwhile, security flaws of contracts have led to huge pecuniary losses and destroyed the ecological stability of contract layer on Blockchain. It is thus an emerging yet crucial issue to effectively and efficiently detect vulnerabilities in contracts. Existing detection methods like Oyente and Securify are mainly based on symbolic execution or analysis. These methods are very time-consuming, as the symbolic execution requires the exploration of all executable paths or the analysis of dependency graphs in a contract. In this work, we propose ContractWard to detect vulnerabilities in smart contracts with machine learning techniques. First, we extract bigram features from simplified operation codes of smart contracts. Second, we employ five machine learning algorithms and two sampling algorithms to build the models. ContractWard is evaluated with 49502 real-world smart contracts running on Ethereum. The experimental results demonstrate the effectiveness and efficiency of ContractWard. The predictive Micro-F1 and Macro-F1 of ContractWard are over 96% and the average detection time is 4 seconds on each smart contract when we use XGBoost for training the models and SMOTETomek for balancing the training sets.
Distributed ledger technology (DLT) is increasingly proposed as a powerful tool to address the social and ecological challenges in the Global South. DLTs are opening up possible futures, one of which is a wave of infrastructure decentralization with common-centric and cosmo-local production. Shared logistics and supply chains for a circular economy, with collaborative and networked ‘flow’ accounting allow the integration of contributive logics as well as the integration of social and ecological externalities, including practical knowledge on resource use limitations linked to planetary boundaries, as an integral part of ecosystems of productive collaboration. Indeed, DLTs remove the need for central intermediaries to validate transaction between parties, who instead place their trust in the encrypted, disintermediated system software. DLTs can be designed as a new unencloseable (non-commodifiable) medium of communication, which could lead to radically new forms of cooperation, organization, and governance. Yet these revolutionary possibilities will not be realized unless technologists consciously and strategically design systems redistributing sovereignty from elites to the people in financial, service and national infrastructures. This paper concludes with a critical examination of the application of DLT in Puerto Rico and how DLTs could alter the production and exchange of “value” in service of a global popular sovereignty.
Blockchain technology as an infrastructure allows an innovational platform for a new transparent and decentralized transaction mechanism for different type of industries and businesses. Different attributes of blockchain technology increase trust through traceability and transparency ability of goods, data and financial resources within any transaction. Regardless of initial uncertainty about this technology, government and many major enterprises and firms have recently examined the adoption and improvement of this technology in several areas of applications, from social, legal and finance industries to manufacturing, design and supply-chain networks. An interesting research problem in this new era is that of determining provenance. At present, goods which are produced and transported using complicated medium supply chains, in this type of supply chain it is impossible to evaluate the provenance of physical goods. We have an interest in the blockchain as there are numerous favored use cases of blockchain especially for provenance tracking. In this paper we review the basics features of the blockchain along with its type like permission less and permissioned blockchain. Then discussed the need of provenance of assets in supplychain as it increase the trust of the customer and proposed a process and architecture for providing the data provenance in supply chain with blockchain using smart contract.
Lin Chen, Lei Xu, Zhimin Gao, Sunny, Ahmed · 6 authors
Recent advances in the blockchain research have been made in two important directions. One is refined resilience analysis utilizing game theory to study the consequences of selfish behaviors of users (miners), and the other is the extension from a linear (chain) structure to a non-linear (graphical) structure for performance improvements, such as IOTA and Graphcoin. The first question that comes to people's minds is what improvements that a blockchain system would see by leveraging these new advances. In this paper, we consider three major metrics for a blockchain system: full verification, scalability, and finality-duration. We { establish a formal framework and} prove that no blockchain system can achieve full verification, high scalability, and low finality-duration simultaneously. We observe that classical blockchain systems like Bitcoin achieves full verification and low finality-duration, Harmony and Ethereum 2.0 achieve low finality-duration and high scalability. As a complementary, we design a non-linear blockchain system that achieves full verification and scalability. We also establish, for the first time, the trade-off between scalability and finality-duration.
Kripto para piyasası kısa dönemde çok hızlı bir gelişim göstermiş hem yatırımcıların hem de akademisyenlerin ilgisini çekmiştir. Bu piyasada en fazla piyasa değerine sahip kripto para birimi Bitcoin’dir. Gerek geleneksel finansal piyasaların işleyişinden farklı bir piyasa işleyişine sahip olması gerekse para yaratma sürecinde farklı bir sistemi kullanması yatırımcılar açısından Bitcoin fiyatlarında değişime yol açan faktörleri anlamayı gerekli kılmaktadır. Bu çalışma ile Bitcoin fiyatlarında haftanın günü anomalisinin varlığının araştırılması amaçlanmıştır. Bitcoin getirilerinde haftanın günü anomalisi, 2013-2019 yıllarına ait günlük fiyatlar kullanılarak asimetrik GARCH modeliyle incelenmiştir. Çalışmadan elde edilen bulgular Bitcoin getirileri üzerinde Pazartesi, Perşembe ve Pazar günlerinin negatif etkileri olduğunu ve en fazla kaybın Perşembe günü gerçekleştiğini ortaya koymuştur.
Bringing Blockchain Technology to Construction Engineering Management - written by Apichart Boonpheng , Dr. Waranon Kongsong , Dr. Nopagon Usahanunth published on 2020/01/21 download full article with reference data and citations
Oxygen is one of the most basic medical therapies we have for acute respiratory illnesses and it has been an established part of medical practice for over 100 years. However, most patients who may benefit from oxygen in low- and middle-income countries will not receive it—either because oxygen is not available or because their need for oxygen is unrecognized. This gap takes an enormous toll, with modeling estimates suggesting that improved pulse oximetry and oxygen access could avert 148 000 under-five child pneumonia deaths annually in the 15 countries with the highest pneumonia burden1. This commentary explores the reasons for this gap, using Nigeria as an illustrative case study in how oxygen access can be improved globally, and concluding with key actions for policy and practice. Nigeria is a large lower middle-income country that ranks second in the number of child pneumonia deaths globally, contributing one-sixth of under-five pneumonia deaths globally.1, 2 Pneumonia causes 18% of under-five deaths in Nigeria, followed by malaria (14%), complications of prematurity (12%), neonatal encephalopathy and trauma (11%), and diarrheal diseases (10%).2 Nigerian studies suggest that hypoxemia affects approximately 14% of children admitted to hospital, including 28% to 49% of children with pneumonia and 22% to 41% of neonates.3-6 Hypoxemia ranks alongside severe acute malnutrition as a major predictor of mortality, with recent data from 12 Nigerian hospitals showing that children with hypoxemia had seven-fold higher risk of death than those who did not.3 Despite the high burden of hypoxemia and increasing recognition of its position as a key sign of illness severity, pulse oximetry, and oxygen therapy have been inadequately used in most Nigerian hospitals. Facility evaluations of Nigerian hospitals have shown that oxygen supply is often not available on pediatric wards, pulse oximeters are uncommonly used outside operating theaters, and healthcare workers lack training on how to use oxygen and pulse oximeters.7, 8 These findings in Nigeria are echoed globally. Hypoxemia is common and deadly,9, 10 yet access to oxygen and pulse oximeters remains limited and healthcare worker skills and confidence using oxygen is low11-14—especially in health centers and smaller hospitals where most sick children first present. At the hospital level, there are three key barriers to improving oxygen access and use. A recent study in 12 south-west Nigerian hospitals found that 92% (11/12) of hospitals had some access to oxygen supplies, 42% (5/12) had oxygen available on pediatric wards at the time of evaluation, and 8% (1/12) used pulse oximetry for pediatric care.7 Testing of 57 oxygen concentrators revealed that 5% (3/57) were producing medical-grade oxygen (defined as >85% purity), and 48% (24/50) of those that turned on and blew gas were simply blowing out air.7 Data from hospitals in northern Nigeria showed that the situation was even worse in these poorer, more rural, locations—11% of hospital pediatric wards had functional oxygen, 2% had pulse oximeters.8 In both regions, procurement of oxygen equipment was haphazard, motivated by price and availability of donated items, with little regard to quality or appropriateness. Hospitals lacked preventive maintenance programs and many technicians reported that they were not aware of the procurement of oxygen equipment until it was brought to them broken for repair.7 Oxygen therapy is unlike most other medications, being administered using equipment and titrated by nurses based on serial clinical assessments (including pulse oximetry). Clinical use of oxygen is not complicated, but healthcare workers do require some basic knowledge and skills. In Nigeria, most nurses receive little training on oxygen, and no training on pulse oximetry, either in nursing school or in-service training—unless they work in anesthetics/theater.7 As such, pulse oximetry is rarely used on pediatric wards, and oxygen (when it is available) is used at excessive flow rates and primarily for those with very obvious respiratory distress; many hypoxemic patients will not receive oxygen.7, 8 Maintaining supply of medical oxygen is expensive, and is made costlier by faulty equipment (eg, leaky cylinders and piping), and poor clinical practices (eg, without pulse oximetry to guide therapy). In Nigeria, oxygen-related patient fees are substantial, typically around ₦3,900 per day7 (USD$21, 2015). These costs fall most heavily on those who are sickest and require longer hospitalization and may result in treatment refusal or discharge against medical advice. In Nigeria (and many other countries), health financing deficiencies result in patients facing substantial out-of-pocket costs in accessing hospital care. The decentralized hospital system in Nigeria gives individual hospitals more autonomy and responsibility for procuring and maintaining medical equipment. However, without technical support or a strong regulatory framework, hospitals often end up with a haphazard array of cheap equipment that they are unable to maintain or repair—exacerbated further by poorly considered equipment donation programs. Nigerian clinicians, hospital administrators, and policymakers have made substantial progress towards improving oxygen access and use. At the national policy level, the Federal Ministry of Health has revised the essential medicines and equipment lists to include oxygen and oxygen-related products, updated the pneumonia clinical guidelines, created a new clinical guideline and hospital policy on oxygen,15 and developed a national strategy for scaling up oxygen nationally.16 This strategy includes the nomination of personnel in the Federal and State Ministries of Health who will be responsible for addressing oxygen access issues in their jurisdiction. Demonstration projects in Nigeria, have shown that the barriers to improving oxygen services can be overcome using existing commercially available equipment, local maintenance teams, and team-based approaches to learning and quality improvement. Results from these projects have demonstrated improved pulse oximetry use on pediatric wards (from <20% to >75%), improved oxygen provision to hypoxaemic children (from <20% to >85%), and reduced mortality from child pneumonia.17, 18 Global policies have also shifted to better support oxygen systems strengthening. In 2013, WHO/UNICEF added oxygen to the Global Action Plan for Pneumonia and Diarrhea, correcting an omission from the first edition.19, 20 This establishes oxygen therapy as a core treatment in the Protect, Prevent, Treat framework (Figure 1). In the past 4 years, the WHO has revised the Model List of Essential Medicines for Children to include oxygen for the treatment of hypoxemia in children,21 published technical specifications for concentrators22 and other oxygen therapy devices,23 and released a new oxygen clinical guidelines for children24—all of which have been used and adapted by Nigeria and other countries. Oxygen therapy is an essential medical therapy for hospital care and should be recognized as a cost-effective investment for improving health care quality and health outcomes. We identify the following key opportunities for improving oxygen therapy for children globally. First, existing evidence shows that improving oxygen systems is a cost-effective intervention that improves the quality of health services and health outcomes. Just as healthcare workers understand the value of oxygen as a basic medical therapy, policy-makers should now be able to recognize that oxygen is a sound financial investment that will make health services better overall. Better oxygen systems should not only improve access to oxygen therapy but also strengthen broader hospital quality of care systems and stimulate the adoption of other essential health technologies as well. Second, we know enough to enact national-scale implementation of improved oxygen systems. Experiences from Nigeria, Ethiopia, Papua New Guinea, and elsewhere, have identified contextual challenges and solutions to improving oxygen systems. These solutions will not be situated within vertically structured programming, but by accepting oxygen therapy as a basic hospital service within a universal health coverage agenda. Policymakers and program managers can be guided by policy documents and technical specifications from WHO and UNICEF22-24 and Every Breath Counts and United for Oxygen consortiums. However, national oxygen strategies must adopt this guidance to local contexts, defining specific responsibilities for those involved in pharmaceutical, medical device, and financing services. Third, pulse oximetry is a low-cost, relatively easily implemented, component of oxygen systems. Essential to the identification of hypoxemia, pulse oximetry is also embraced by healthcare workers as a valuable tool in assessing and monitoring sick patients that improves the quality of care more generally. As such, pulse oximetry scale-up represents “low-hanging fruit” for improving hospital care, and may also play an important role in facilitating referral from primary care.14, 25 Fourth, existing oxygen technologies are suboptimal in hot, humid, dusty conditions, or environments that lack strong maintenance structures. We need better technology to provide reliable oxygen in places where power failures are common, produce and store oxygen locally, and efficiently deliver oxygen from the oxygen source to patients. Fifth, previous studies have demonstrated the mortality impact of pulse oximetry and improved oxygen systems for young children with pneumonia, but little data exist for other children or neonates (in whom oxygen is also used commonly). The neonatal cohort represents a particular group of interest, as they can suffer adverse effects from administration of excessive oxygen (eg, retinopathy of prematurity, bronchopulmonary dysplasia).26, 27 Oxygen therapy is an essential medical therapy that is poorly available and suboptimally used in many low- and middle-income countries. Recent policy and programmatic experience in Nigeria has shown how oxygen services can be improved for the benefit of children and health services. Hamish Graham, Ayobami A. Bakare, Chizoba Fashanu, Owens Wiwa, Trevor Duke, and Adegoke G. Falade received payment for services related to this paper from the Bill and Melinda Gates Foundation (OPP1123577 and OPP1133417). HG drafted the manuscript. AAB, CF, OQ, TD, and AGF provided substantial comments to the writing of the manuscript. All authors read and approved the final manuscript.
Deepak Puthal, Saraju P. Mohanty, Venkata P. Yanambaka, Elias Kougianos
In today's connected world, resource constrained devices are deployed for sensing and decision making applications, ranging from smart cities to environmental monitoring. Those recourse constrained devices are connected to create real-time distributed networks popularly known as the Internet of Things (IoT), fog computing and edge computing. The blockchain is gaining a lot of interest in these domains to secure the system by ignoring centralized dependencies, where proof-of-work (PoW) plays a vital role to make the whole security solution decentralized. Due to the resource limitations of the devices, PoW is not suitable for blockchain-based security solutions. This paper presents a novel consensus algorithm called Proof-of-Authentication (PoAh), which introduces a cryptographic authentication mechanism to replace PoW for resource constrained devices, and to make the blockchain application-specific. PoAh is thus suitable for private as well as permissioned blockchains. Further, PoAh not only secures the systems, but also maintains system sustainability and scalability. The proposed consensus algorithm is evaluated theoretically in simulation scenarios, and in real-time hardware testbeds to validate its performance. Finally, PoAh and its integration with the blockchain in the IoT and edge computing scenarios is discussed. The proposed PoAh, while running in limited computer resources (e.g. single-board computing devices like the Raspberry Pi) has a latency in the order of 3 secs.
Nicola Marotta, Antonio Ammendolia, Cinzia Marinaro, Andrea Demeco · 6 authors
BACKGROUND: Stroke is the third cause of long term disability worldwide and its rehabilitation program must to have into account all aspects of disability. International research and politics increasingly study the relationship between disability and the direct costs associated with living with a disability. OBJECTIVE: Using the ICF, this article provides a correlation between financial assets and disability in participation and activities, in a context such as the Italian one where there is a twenty-year decentralization of the national health system Methods. At the University of Catanzaro, in southern Italy, n=130 ICF checklists of stroke patients were analyzed at 6 months from the end of the rehabilitation treatment. Financial assets domains in environment and nine domains in participation and activities were correlated, in order to evaluate the relationship between familiar economic condition and disability. RESULTS: Pearson's r test (t = -6.6515, df = 25, p-value<0.05) showed a significant correlation of 0.79. Multiple R-squared was 0.639 and an we reported an Adjusted R-squared of 0.6245 (p<0.05). Thus, about 62% of the increase of the all considered disability qualifiers in participation and activities in ICF checklist can be explained by a lower financial income. CONCLUSIONS: In a regional context (Calabria) of an European country (Italy) with a national health system, thanks to the ICF it can be assumed that with the decrease of the financial income, the gap in participation of activities increases.
With the recent popularity of Blockchain and other Distributed Ledger Technologies (DLT), blockchain enabled smart contract applications has attracted increased research focus. However, the immutability of the blocks, where the smart contracts are stored, causes conflicts with the traditional Software Development Life Cycle (SDLC) models usually followed by software engineers. This clearly shows the unsuitability of the application of SDLC in designing blockchain enabled smart contract based applications. This research article addresses this current problem by first exploring the six traditional SDLC models, clearly identifying the conflicts in a table with the application of smart contracts and advocates that there is an urgent need to develop new standard model(s) to address the arising issues. The concept of both block immutability and contract is introduced. This is further set in a historical context from legacy smart contracts and blockchain enabled smart contracts extending to the difference between "shallow smart contracts" and "deep smart contracts". To conclude, the traditional SDLC models are unsuitable for blockchain enabled smart contract-based applications.
Abstract Port Knocking is a method for authenticating clients through a closed stance firewall, and authorising their requested actions, enabling severs to offer services to authenticated clients, without opening ports on the firewall. Advances in port knocking have resulted in an increase in complexity in design, preventing port knocking solutions from realising their potential. This paper proposes a novel port knocking solution, named Crucible, which is a secure method of authentication, with high usability and features of stealth, allowing servers and services to remain hidden and protected. Crucible is a stateless solution, only requiring the client memorise a command, the server’s IP and a chosen password. The solution is forwarded as a method for protecting servers against attacks ranging from port scans, to zero-day exploitation. To act as a random oracle for both client and server, cryptographic hashes were generated through chaotic systems.
As the largest public blockchain-based platform supporting smart contracts, Ethereum has accumulated a large number of user transaction records since its debut in 2014. Analysis of Ethereum transaction records, however, is still relatively unexplored till now. Modeling the transaction records as a static simple graph, existing methods are unable to accurately characterize the temporal and multiplex features of the edges. In this brief, we first model the Ethereum transaction records as a complex network by incorporating time and amount features of the transactions, and then design several flexible temporal walk strategies for random-walk based graph representation of this large-scale network. Experiments of temporal link prediction on real Ethereum data demonstrate that temporal information and multiplicity characteristic of edges are indispensable for accurate modeling and understanding of Ethereum transaction networks.